1. Field of the Invention
The present invention relates to an industrially advantageous apparatus that chemically decomposes cut piece wastes of polyurethane resin in the molding and working process and product wastes thereof after their use, and recovers the decomposed polyurethane resin as a polyamine compound and/or a polyol compound that are the materials of the polyurethane resin.
2. Description of the Related Art
Polyurethane resin is massively used in the form of soft, semi-rigid, and rigid urethane foams in a variety of fields as the cushioning materials, for example, for sofas, beds, other furniture, and seats in vehicles and the thermal insulating materials, for example, for the refrigerators. The polyurethane resin is also used in the form of elastomers, for example, for shoe bottoms, tires, and belts. As the greater importance is placed on protection of the resources and preservation of the environment, a variety of techniques have been proposed and studied to attain the recycle and the reuse of various plastics including polyurethane resin.
Known recycling procedures of polyurethane resin are roughly classified into three; that is, the material recycling technique, the chemical recycling technique, and the energy recycling technique. One example of the material recycling technique reclaims the used polyurethane foams as the cushioning materials by means of re-bonding or compression molding. Another example crushes the used polyurethane foams and elastomers and mixes the crushed resin as a tiller with a new material. The chemical recycling technique decomposes the polyurethane resin to its raw materials or to compounds that can be used as the raw materials, and reuses the raw materials and the compounds. The chemical recycling may be attained, for example, through glycol decomposition, amine decomposition, or hydrolysis. The energy recycling technique utilizes the used polyurethane resin directly as a fuel or as an energy resource to give steam or a gaseous fuel.
The material recycling technique, however, possibly causes problems of the poor quality of resulting products and thus limits the range of application. The energy recycling technique possibly leads to environmental problems, such as generation of harmful substances through the combustion. The chemical recycling technique is, on the other hand, applicable to a wide variety of compounds to be recovered. By taking into account these merits and demerits, it has highly been demanded to develop an improved apparatus to attain the chemical recycling technique economically on the industrial base.
The glycol decomposition process or the amine decomposition process applied for the chemical recycling technique cuts the urethane bond, the biuret bond and the allophanate bond, which are relatively easily decomposable among all the bonds, such as the urethane bond, the urea bond, the biuret bond, and the allophanate bond, that are present in the polyurethane resin, by means of the glycol compound or the amine compound, thereby decomposing the polyurethane resin to low molecular weight substances and generating a liquid decomposition product. The glycol compound or the amine compound used as the decomposer, however, newly generates urethane bonds and urea bonds and is linked to the decomposition product by these bond. Such decomposition processes can thus not decompose the polyurethane resin to a polyol compound as a starting material of the polyurethane resin, and a polyamine as an intermediate compound of polyisocyanate. The recovered substances are accordingly usable for only the limited applications.
The applicant of the present invention has proposed a method of hydrolyzing polyurethane resin using high-temperature high-pressure liquid water as the decomposer (WO98/34909). This proposed technique heats polyurethane foam to decrease its volume and supplies the solid polyurethane foam of the reduced volume to hydrolysis means. A further improvement in material supply means is required to provide an efficient continuous flow apparatus for carrying out the hydrolysis of polyurethane resin on the industrial base. Problems of contaminating the reaction passage with foreign matters and blocking the reaction passage may arise, for example, in the process of recycling shredder dust of the seats in the vehicles, which is generally mixture of fibers and resin.
An object of the present invention is thus to provide an apparatus of decomposition and recovery that continuously decomposes and recovers polyurethane resin with high-temperature high-pressure water or supercritical water, which advantageously reduces the required energy cost, reduces the size of the whole apparatus, removes foreign substances from the shredder dust, and decreases the required quantities of substances for decomposition, and the like.
At least part of the above and the other related objects is realized by an apparatus for decomposing a polyurethane resin and recovering the decomposed polyurethane resin as a polyamine compound and/or a polyol compound. The apparatus includes: a first reactor that decomposes the polyurethane resin as a target compound of hydrolysis decomposition; a second reactor that hydrolyzes the decomposed target compound with either one of supercritical water and high-temperature high-pressure water to a decomposition product mixture; a water supplier that feeds of either one of supercritical water and high-temperature high-pressure water to the reactor; and a post-processor that causes the decomposition product mixture discharged from the reactor to be subjected to a post process, such as dehydration, addition, distillation, separation, and liquid separation, to recover the polyamine compound and/or the polyol compound.
The apparatus of the present invention decomposes polyurethane resin and feeds the decomposed polyurethane resin to the second reactor. This arrangement enables continuous decomposition. Compared with the prior art apparatus that hydrolyzes solid polyurethane resin in a reactor, this arrangement relieves the conditions of the hydrolysis. This advantageously decreases the water addition ratio and reduces the reaction time, thereby reducing the volume of the reactor, lowering the required level of the performance of the water supply unit, and eventually reducing the recycling cost.